The use of probe vehicles to collect and transmit information about current traffic conditions for use in conjunction with a traffic information and management system has been proposed previously. Traffic probe vehicles are vehicles that are specifically equipped to obtain, store and transmit traffic-related information. They may comprise vehicles that are specifically designated and equipped for the purpose of providing such information, or vehicles that are being used in ordinary service, such as commercial vehicles, fleet vehicles or passenger vehicles, and that are also equipped to obtain, store and transmit traffic-related information in conjunction with such service.
Relatively low concentrations (e.g. less than 10%) of probe vehicles in an entire population of vehicles can provide significant information on traffic conditions on the various types of roadways in a particular geographic area. Estimates of traffic speeds and travel times based on information received from probe vehicles can be more accurate, and provide traffic information having higher resolution and greater geographic coverage than that available from other types of traffic information systems.
A significant challenge associated with acquiring and processing real-time traffic information from probe vehicles is the cost of transmitting voluminous raw data from the vehicles to a traffic information system. While estimates of these costs have been reduced dramatically as the costs of wireless data transmission have been reduced, nevertheless, it is believed that the economic viability of probe-based traffic information systems will require the implementation of communication methods which reduce the volume of information communicated and the frequency of communication, thereby reducing the communication-related expenses. Methods which have been suggested to reduce the amount of data transmitted have generally included both data compression and data reduction algorithms. While implementation and improvement of both methods are desirable, improvements in data reduction methods are particularly desirable if they can typically be implemented in existing hardware and vehicular systems relatively quickly and with a relatively smaller number of changes, thereby reducing or eliminating the need for extensive and costly modifications, qualifications and other testing.
When using probe vehicle based traffic information systems, each vehicle independently collects, stores, and transmits its own raw data according to a predetermined data storage and transmission algorithm. Therefore, any strategy or method for reducing the data transmitted must ultimately be implemented by the individual vehicle.
While various approaches have been suggested to enable the collection, storage, transmission and use of probe vehicle data, including selective transmission schemes, such approaches have certain disadvantages in that they typically require the use of dedicated hardware, software or both, or do not provide sufficient flexibility or selectivity with regard to the prioritization, collection or transmission of traffic information for a particular roadway, or require specialized and expensive data collection or processing systems, or combinations of these limitations.
Based on the limitations noted above, none of the existing methods are optimal for providing real-time traffic information about a traffic network comprising a large number (i.e., many thousands and perhaps millions) of individually owned and operated vehicles that are free to drive anywhere at any time over a network of hundreds or perhaps thousands of roadways as is the situation in many major metropolitan areas or traffic corridors.
Therefore, it is desirable to develop a method of obtaining storing and communicating traffic information that reduces the amount of information that must be communicated, and hence the associated communication costs, between the probe vehicles and the traffic information system and that utilizes existing vehicle systems, such as on-board global positioning systems, cellular communications systems and vehicle control systems to reduce the cost of implementing such a method.